This application relates to dispensing.
Many applications call for an automatic mechanism that dispenses a desired amount of a material. For example, in an automatic assembly line used in producing semiconductor-based electronic circuits, when an electronic part such as a chip resistor, a capacitor, or a packaged integrated circuit (xe2x80x9cICxe2x80x9d) is to be mounted onto a substrate having a circuit pattern formed thereon, creamy solder is deposited in a selected position on the substrate by use of a dispenser and then the electronic part is automatically mounted in the selected position by use of a chip mounter.
Other applications use solder spheres, also known as solder balls, instead of creamy solder or as electrical connection points known as leads. For example, high density I/O chip carriers use ball grid array packages (xe2x80x9cBGAsxe2x80x9d) that have a high I/O count at a relatively coarse pitch. Typically, the solder balls are dispensed in a predetermined pattern on or in an electronic part or circuit. In some cases, the electronic part or circuit can be rendered inoperative even if only a single solder ball is missing from the pattern after an attempt has been made to dispense solder balls in the pattern on the part or circuit. In such a case, the only means (or the only cost effective means) available for dispensing the solder balls may be a device, such as a stencil having apertures as disclosed in U.S. Pat. No. 5,431,332 which is incorporated by reference, that is provided for dispensing a large amount of solder balls at once on a clean substrate, i.e., a substrate having no solder balls. If so, it may be impossible or impractical to use the available device to dispense a single solder ball, and therefore it may be necessary to discard the part that is missing the single solder ball.
Apparatus and a method are provided for dispensing. In particular, dispensing apparatus is provided for dispensing items. The dispensing apparatus includes a dispensing outlet and an item holder having item holding areas and being movably disposed to position the item holding areas one at a time in sequence over the dispensing outlet so that when one of the item holding areas is positioned over the dispensing outlet, the other item holding areas are not disposed over the dispensing outlet. The dispensing apparatus further includes a blocker disposed over the item holder opposite the dispensing outlet, the blocker blocking access to the dispensing outlet from directly above the item holder when the item holder positions one of the item holding areas over the dispensing outlet. The apparatus and method allow the dispensing of items to be controlled so that only one of the items is dispensed at a time. An item such as a solder ball can be dispensed at a selected destination by positioning the dispensing outlet appropriately with respect to the selected destination (e.g., above a selected circuit board location) and then rotating the item holder to bring the item to the dispensing outlet.
Other features and advantages will become apparent from the following description, including the drawings, and from the claims.